Core for electric transformers



March 24, 1931. J. w. swl-:NDsEN CORE FOR ELEC-TRICTRANSFORMERS Filed Jan. 15, 1950 gyr 'M CII Patented Mar. 24, 1931 PATENT OFFICE JOHAN WALFRED SWENDSEN, A0F OSLO, NORWAY CORE FOR ELECTRIC TRANSFORMEBS Application led January 15, 1930, Serial No. 421,018, and in Germany January 16, 1929.

The present invention relates to electric transformers, and its object is primarily to reduce the cost of production of transformers, and this is accomplished by making all the parts ofthe iron cores for the transformer entirel y on a manufacturing principle i. e. with- :t unnecessary handwork.

According tothis invention such method of manufacturing of the iron cores is made possible by assembling the iron core of the transformer from a number of sections, each of which is produced by winding a long con-` tinuous iron band in the form of a spiral coil.

In order to make this invention easily understood it will be described in the following with referencel to the drawing, showing a preferred embodiment of the invention.

In the drawing:

Fig. l illustrates a view of the transformer without the conventional oil container, and the figure illustrates the transformer partly in section.

Fig. 2 is a cross section through the transformer at the line II-II of Fig. 1.

Fig. 3 is a cross section of the transformer at the line IIl-III of Fig. 1.

In the drawing, the transformer core con sist-s of four parts 1, 2, 3 and 4, of which parts 1 and 2 are the cores proper for the two electric coils 5and 6. These cores 1 and 2 are.- as can Veasily be seen in the drawing-made by winding an iron ribbon in the form of a flattened spiral. Between each layer of the iron band, a layer of suitable insulation, as forinstance paper, .may be placed, while the core is being wound. The magnetic circuit between the two cores 1 and 2 is completed by means of two intermediate core pieces 3 and 4. These pieces are also made by winding almetal ribbon in the form of a flattened s 1ra pWhen producing the two last mentioned core pieces 3 and 4, it is of very great importance to prevent that a closed circuit for the eddy current be established around the axis of the core piece. If such should be the case, enormous heating and losses will occur in the said pieces 3 and 4. To prevent this, it is necessary that the iron band of these date.

connecting pieces do not form a continuous spiral.

According to the invention these pieces are therefore made by winding a metal ribbon in the form of a spiral, from which thereafter a suitable sector is removed, thereby breaking the continuous spiral winding and producing a core section, constituted of a number of curved laminated layers.

The inventor has found that a very practical and cheap method of making the sec tions 3 and 4 is to make two of these pieces .at the same time in one piece, which after b eing finished is cut in two. These two sections will then receive a cross sectional form, as will appear from Fig. 2. The four pieces formmg the whole iron core of the transformer may preferably be held together by bolts'7 and 8, comprising suitably arranged nuts for tightening purposes. y I A transformer according to this invention 1s especially adapted for the use of coils of that type which is described in patent application Serial No. 421,019 tiled on the same Claims: 1. A transformer core having a plurality of straight portions adapted to carry current conducting coils, said portions being made of long iron ribbons, Wound into a flattened spi-ral, and intermedi-ate portions connecting the ends of said two "straight portions with each other to form a closed magnetic circuit, said intermediate portions consisting of a spirally wound metal ribbon, a radial cut beingl made through all the layers. to prevent undue` eddy currents to be generated.

2. A transformer core having a plurality of straight portions adapted `to carry current conductmg coils, said portions being made of long iron ribbons, wound into a flattened spirahand intermediate portions connecting the ends of said two straight portions with each other to form a closed magnetic cir-f cuit, said intermediate portions consisting each of half a longish flat spiral wound ofa continuous iron ribbon.

3. An electric transformer comprising a current conducting coil and an iron core through said coil, said core consisting of a long strip of metal being Wound in a, Hat compact spiral coil, the windings of .which pass twice through the center of the current coil with their axis vertical to the axis of the said current coil.

In testimony whereof I have signed my name unto this specification.

JOHAN WALFRED SVYENDSEN.A 

